Prismatic mirror



Sept 17, 1968 J. G. wARHol. 3,402,004

PRI SMATIC MIRROR Filed Oct. l2, 1964 Z4 y i -27 ufo/2x2 6mp/UZ BY MAX R. KQAUS ATTK 7 242 United States Patent O 3,402,004 PRISMATIC MIRROR John G. Warhol, Oak Park, Mich., assignor, by mesne assignments, to Nelmor Corporation, Harper Woods, Mich., a corporation of Illinois v Filed Oct. 12, 1964, Ser. No. 403,102 1 Claim. (Cl. 350-281) ABSTRACT OF THE DISCLOSURE A non-shatterable mechanically strong rear view mirror for automotive use is provided by having fiat pieces of glass in non-parallel relationship and maintained'in position by having cast therebetween a thermosettmg transparent plastic. The plastic is a mixture of polyester and acrylic compounds including a catalyst hardening agent to promote setting.

This invention relates to improvements in prismatic mirrors and to the process and method for forming same.

Under present day practice, prismatic mirrors are produced from a single piece of plate glass, with one of the sides being coated and the uncoated side being ground to provide an angled surface to produce a wedge-shaped plate in vertical section. This grinding process 1s a very slow and expensive procedure and adds greatly to the cost of the finished product. By virtue of the special grinding machines which are necessary and the slow procedure, a limited number of such mirrors may be prolduced with a given machine, thus slowing down production and increasing the cost.

The present invention provides a new and improved type of prismatic mirror which may be produced at approximately one-half the cost of producing the present prismatic mirrors, and also includes a process or method which does not require the expensive and costly grinding equipment heretofore necessary, thereby facilitating increased production at reduced costs. In addition, a more efficient and effective prismatic mirror is produced than that now produced in commercial practice.

Other objects will become apparent as this description progresses.

The drawings will illustrate diagrammatically the process or method for forming the prismatic mirror of this invention.

In the drawings:

FIG. l is a perspective view of a rear view mirror formed in accordance with this invention.

FIG. 2 is a sectional view taken on lines 2-2 of FIG. 1.

FIG. 3 is a perspective view of the rear panel coated with a reective material.

FIG. 4 is a perspective view of the front panel.

FIG. 5 is a view of the two panels positioned relative to each other as they would be in the mold when the bonding material is introduced.

FIG. 6 is a sectional view of the panels in a mold cavity, showing the process in the formation of the structure in accordance with this invention.

FIG. 7 is an elevational view taken on lines 7-7 of FIG. 6, and

FIG. 8 is a sectional view taken on lines similar to FIG. 2 of a modified construction.

In the embodiment shown in FIGS. 1 to 7, which will be first described, two panels of glass are used, the front panel being identified by the numeral 10 and the rear panel identified by the numeral 12. Both of these panels are ordinary picture frame glass, which is a clear colorless glass, each having a thickness of approximately .060. If it is intended that the mirror be used for a rear view 3,402,004 Patented Sept. 17, 1968 ICC mirror for automobiles then the panels or strips are precut to the generally oblong shape shown.

The front panel 10 is not treated in any particular manner. The rear panel 12, which is of the same size and dimension as the front panel 10, is coated and luminized to provide a film of a reective surface, indicated by the numeral 14. It may be coated or luminized or treated in an equivalent manner similar to a vacuum deposition metallic coating or first surface chrome, which is a well-known process in the industry. The rear panel 12 is positioned with the luminized surface 14 on the inside facing the front panel 10. There are other reflective surfaces which may be used, such as chrome or the like, all of which are well-known.

The two panels 10 and 12 are positioned with respect to each other, as shown in FIG. 5, in which they are disposed at an angle relative to each other to form a prism structure. The two glass panels touch each other at the bottom and are spaced apart adjacent their upper ends. The angular separation at the top is approximately 3.5 degrees, this measurement being taken from the inside of the film coating 14 to the front wall of the front panel 10. The 3.5 degree angular separation, as aforesaid, is the preferred position, although it will be understood that it can be more `or less than 3.5 degrees.

With the two panels 10 and 12 held in the angular position shown, by the means hereinafter described and best shown in FIGS. 6 and 7, the space between the panels is filled with a bonding material 16 which is a plastic composition, more particularly hereinafter described. To position the two panes or panels 10 and 12 in the aforementioned manner they are placed in a fixture, which is best shown in FIGS. 6 and 7, and identified generally by the numeral 20.

The fixture 20 comprises a pair of mold sections 22 hinged together at the bottom thereof as at 24. A split silicone rubber mold or lining 26 is mounted in the mold sections. Each of the panel molds or linings 26 is recessed as at 27 to accommodate its respective panel 10 or 12. Each mold section 22 has openings 28 which are connected to conduits 29, which in turn are connected to vacuum producing means (not shown). Openings 28 register with openings 30 in the silicone rubber mold or equivalent lining 26. Other openings 32 are provided for introducing air into the mold cavity. The mold sections are provided with a central inlet opening 34 at the top thereof which communicates with the mold cavity. A funnel 36 and a bafiie 37 are connected to said central opening 34 and it is through the funnel and bafiie that the plastic composition 16 is fed into the mold cavity.

The two glass panels 10 and 12 are positioned in the mold cavities and when the mold cavities are closed the vacuum introduced into the mold through the conduits 29, openings 28 and 30 hold the two panels 10 and 12 in their angular position, shown in FIG. 6. Contact adhesive spots may be used in place of vacuum, with the adhesive spots located in the same positions as the openings 30 in the silicone rubber, as shown in FIG. 6, and openings 32 could be used for the air pressure to release the finished product from the mold. The adhesive spots would protrude far enough to contact the glass. When the mold sections are inclosed position the edges of the mold are sealed and the plastic bonding material that is introduced -between the panels 10 and 12 will not escape from between the two panels.

The bonding material 16 which is to fill the void between the two panels 10 and 12 is a plastic composition. One extremely well suited for such use is a product known as Castolite, sold by the Castolite Company of Woodstock, Ill. The plastic composition used belongs to the thermosetting class of plastics and is composed of polyester and acrylic compounds. These ccmpounds are liquefied and the use of a catalyst hardener speeds the setting. If necessary, a polyester alone can be used. The plastic composition is of such character that heat will not melt it; in fact, it will not soften appreciably at temperatures below 250 F. The higher temperatures will tend to harden the composition rather than soften it.

Before introducing the Castolite material into the mold, as aforementioned, it is mixed with a hardener which may be a conventional chemical composition, It is important that in the mixing of the hardener with the Castolite material that all the bubbles are eliminated from the two materials. One manner of eliminating the bubbles in the mixing and handling is to place the Castolite material in a container and then add the hardening material thereto and thenk roll the container with the materials therein so that the hardener mixes with the Castolite material. This procedure eliminates bubbles in the mixed composition. After the composition material has been mixed it is then ready to be introduced into the mold, as aforementioned.

This admixed bonding composition 16 is introduced into the mold by a gravity How through the funnel 36 and baffle, and as the composition enters between the panes or panels and 12 it will fill from the bottom up and displace the air trapped between the two panes, thus, all air, bubbles, or other things of that character will not be present in the material between the panes or panels. As the material flows by gravity it will first strike the baffle, which allows the composition material to enter the cavity at a faster rate of speed than would be possible without the use of a baffle.

To accelerate the hardening of the admixed material in the void between the panels, one of the panels can be heated and this will accelerate the hardening process. As previously stated, one of the characteristics of this Castolite material is that higher temperatures tend to harden rather than soften the material, thus, heat will accelerate the hardening process. Under normal conditions, without the application of heat, it is estimated that it would take approximately ten hours to harden, however, with the use of heat the hardening and setting will take place at a much more rapid rate. At no time is pressure applied against the two panes or panels to squeeze the bonded material therebetween. It is allowed to harden, as aforementioned, without any pressure between the panes or panels. After the hardening has taken place, the laminated prismatic mirror is removed from the mold and the outer edges of same is sanded and cleaned by any means, such as a grinding wheel, sand i grinder, buffer, or the like, and the unit is then ready for use.

Aside from the increased production possible by this process, and the reduced cost, the resultant product has the advantage of an increased safety factor, in that since this is a laminated product in which the glass panes are bonded to a plastic material the glass will not splinter when in a crash, as would happen with the conventional prismatic mirror. Instead it will crack, with the Cracked pieces adhering to the plastic composition and thereby reduce the danger element to the occupant of the car.

Another important advantage derived from this process is the increase in light reflectivity by virtue of the plastic material reflecting the light rays faster than the conventional glass. Conventional prismatic mirrors produce between two-thirds and three-quarters returned light reflection. The present invention increases the light reflectivity, which means the returned light is closer to the maximum of A modified prismatic mirror is shown in FIG. 8. In the modified construction, designated generally by the numeral 40, there is eliminated the second pane of glass and the reflective surface is affixed to the rear side of the plastic composition. In said construction there is a pane of glass 42, identical to pane 10 described in connection with FIGS. 1 to 7. The plastic composition Castolite, which is the same as that previously described and heretofore identified as 16, and which is here designated as 16', is affixed to the rear of the glass, and the shape of the plastic composition is angular or wedge-shaped, as shown. The rear face of said plastic composition is coated or has a chrome deposition on plastic, as indicated at 14', to provide a reflective surface, similar to the reflective surface 14 previously described. The manner of applying the plastic composition 16' to the pane of glass 42 is similar to that previously described in connection with the process of the elements shown in the previous figures and hence will not be redescribed.

It will be understood that various changes and modifications may be made from the foregoing without departing from the spirit and scope of the appended claims.

What is claimed is:

1. A prismatic mirror for use as a rear view mirror for automotive vehicles, said mirror comprising a transparent front glass plate of uniform thickness, a rear glass plate of uniform thickness having a reflecting coating on one face thereof, said glass plates being disposed in nonparallel laterally offset relationship to provide a prism structure, and a cast thermosetting transparent plastic material disposed between the opposing non-parallel faces of said glass plates with the reflecting surface of the rear plate being disposed to receive light falling on the front plate passing through said plastic, said plastic material consisting of a mixture of polyester and acrylic compounds having a catalyst hardener therein for accelerating setting, said mirror structure being substantially free of air bubbles and forming a laminated non-shatterable but strong construction and resistant to temperatures up to about 250 F. wherein the front and rear glass plates have an angle therebetween of substantially 3.5.

References Cited UNITED STATES PATENTS 1,949,138 2/1934 Bell 350-281 2,558,848 7/1931 Harrison 350-278 X 2,887,424 5/1959 Lanberg 350-320 X 3,111,570 11/1963 Strang et al. 350-178 X FOREIGN PATENTS 557,515 11/1943 Great Britain. 582,248 11/1946 Great Britain. 505,836 5/1939 Great Britain.

DAVID H. RUBIN, Primary Examiner.

P. R. GILLIAM, Assistant Examiner. 

